Punch presses are typically configured to hold a plurality of tools for forming a variety of shapes and sizes of indentations and/or holes in sheet workpieces, e.g., formed of sheet metal. Tools of this sort commonly include at least one punch assembly and corresponding die. In a multiple station turret punch press, a rotatable turret is often used for holding a plurality of punch assemblies above a workpiece support surface, while a corresponding plurality of die-receiving frames are located below the workpiece support surface. In some cases, once a first tool set has been used, it is exchanged for a second tool set, and then a third, and so on. In some cases, the machine tool includes an elongated rail for storing the tool set in cartridges. The cartridges, for example, can be slidably engaged with the rail such that they can be slid back and forth to and from the mounting position. Once a first workpiece has been fully processed using the desired sequence of tool sets, a second workpiece may be processed, in some cases beginning again with the first tool set.
A conventional punch assembly includes a punch guide and a punch body or holder, as well as a punch tip, which may be either fixedly or releasably attached to the punch body. The punch body and tip are slidably engaged within the punch guide for reciprocal, axial movement along a central longitudinal axis of the punch guide. Such a punch assembly and a corresponding die are mounted in a press and located in a working position of the press, e.g., beneath the ram (or integrally connected to the ram). As such, when downward force is provided on the ram, the punch tip is driven out from the punch guide in response and through an opening in a stripper plate, in order to form an indentation or a hole through a sheet workpiece. The stripper plate, which is attached to an end of the punch guide, prevents the workpiece from following the punch tip, upon its retraction back into the punch guide.
Those skilled in the art appreciate that punch assemblies require regular maintenance and modification, for example, to sharpen or replace worn punch tips, and to replace punch tips of one shape (or footprint) with those of an alternate shape for differing pressing operations. In the case of punch tips configured to be releasably attached to punch bodies, such tips are generally assembly-specific, i.e., not interchangeable with other punch assembly types. As a result, regular maintenance and modification on differing punch assemblies can involve a great deal of time and expense with regard to keeping sufficient stock of replacement punch tips for each of the assemblies.